Probiotics and Prebiotics—Should They Be Used Together?

By Whitney Crouch, RDN, CLT

Probiotics. We’ve all heard the buzzword, and many are now familiar with the term the “good guys” in the gut…but what do they do? What are they, exactly?

Do prebiotics act alongside probiotics? How are they beneficial to the host or their gut microbiota? These are questions that have been explored recently, and the answers are only the beginning of where the science of prebiotics and probiotics will go.

Probiotics

It has been known for some time that the human body is inhabited by at least 10 times more bacteria than the number of human cells in the body, and that the majority of those bacteria are found in the human gastrointestinal tract.1-2

According to the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO), probiotics are “live microorganisms which when administered in adequate amounts confer a health benefit on the host.”3

Health benefits have mainly been demonstrated for specific probiotic strains of the following genera: Lactobacillus, Bifidobacterium, Saccharomyces, Enterococcus, Streptococcus, Pediococcus, Leuconostoc, Bacillus, Escherichia. Health benefits are strain- and dose-specific and include a wide range of support including (but not limited to) skin, gut, immune, and vaginal health.4

The body of scientific evidence is growing rapidly to support the use of probiotics in health management, including approaches to increase the efficacy of probiotics. One such method is using prebiotics at the same time.

Prebiotics

In 2016, a panel of experts convened to update the definition of prebiotics—substrates that are selectively utilized by host microorganisms conferring a health benefit.5 Prebiotics are more diverse than you may know, including certain kinds of fats (conjugated linoleic acid [CLA] or polyunsaturated fatty acids [PUFAs]), phenolics, and phytochemicals, to name a few; however, the most well-known and studied prebiotics are typically derived from nondigestible fibers and include a family of compounds called oligosaccharides.

Prebiotics are not only the familiar carbohydrates that we once knew, like fructans (fructooligosaccharides [FOS] and inulin), galactans (galactooligosaccharides [GOS]), and isomaltooligosaccharides (IMOs);5 the definition has expanded to include new names on the market and even includes human milk oligosaccharides (HMOs), a natural component of human breastmilk.

To be considered a prebiotic, these bioactives need to fit three criteria:5

The two most investigated prebiotics are fructans and galactans. Fructans include inulin and FOS, which can be found in many common foods, including blue agave, chicory root, garlic, onion, Jerusalem artichokes, leeks, asparagus, dandelion greens, and bananas.6 GOS, a functional alternative to HMOs, are found in infant formulas and are also found in seaweed and legumes like chickpeas, lentils, kidney beans, and green peas.7

Whereas the average dietary fiber supports the health of both the “good” and “bad” microbiota in our guts, prebiotics are more targeted in that they selectively support the microbiota that support the host—the humans or animals that the microorganisms live in.

How do prebiotics work to support probiotics and human health?

Prebiotics are fermented by human gut microbiota (remember: probiotics help colonize the gut with healthy microbes) into short-chain fatty acids (SCFAs) acetate, propionate, and butyrate. SCFAs are increasingly recognized as signaling molecules that mediate the interaction between the diet, the gut microbiota, and the host.8 Locally in the gut, SCFAs serve as energy substrates for cells of the colon and play a role in host metabolism.8-9 A fraction of the colon-produced SCFAs reach the systemic circulation and directly affect the function and metabolism of peripheral organs and tissues, such as the liver, the pancreas, adipocytes, immune cells, and skeletal muscle tissue. Studies show that the permeation of SCFAs throughout the body are involved in maintaining glucose and lipid metabolism and may provide an important target for other facets of health as well.9

There are health benefits to be had for individuals consuming probiotics with prebiotic compounds; however, there may be contraindications for some patients. It should be noted that people with sensitivities to fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) should use caution and consult a knowledgeable healthcare practitioner before incorporating higher amounts of prebiotic foods or supplements.

The market for supplements containing prebiotics or pre-/probiotic combinations and the body of research science supporting their clinical use are both growing, with more discoveries and targeted approaches to be revealed. It’s important to choose high-quality supplements to ensure the best symbiotic relationship between pre- and probiotic strains, which in turn can increase the efficacy of this combination.

Hill C et al. Expert consensus document: The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nat Rev Gastroenterol Hepatol. 2014;11(8):506-14.

Whitney Crouch is a Registered Dietitian who received her undergraduate degree in Clinical Nutrition from the University of California, Davis. She has over 10 years of experience across multiple areas of dietetics, specializing in integrative and functional nutrition and food sensitivities. When she’s not creating educational programs or writing about nutrition, she’s spending time with her husband and young son. She’s often found running around the bay near her home with the family’s dog or in the kitchen cooking up new ideas to help her picky eater expand his palate.